When a wireless communication network receives a communication (voice or data including but not limited to audio, video, internet, etc.) for a particular wireless device, the network sends out a page in an attempt to connect to the device. Paging a wireless device incurs network bandwidth costs, however. So, it is desirable to know precisely where the device is when a page is to be sent so that the device can be contacted with a limited number of pages via a small set of base stations, if not a single, precise page via a single base station.
Such knowledge also comes with an associated bandwidth cost since the only way to know where the device is at all times is to frequently update the network with the location of the device. But, this diminishes the battery life of the device, requiring more frequent recharging and increasing the likelihood that the device user will be found with a temporarily unusable device.
Alternatively to maintaining a continuous connection between the network and a device, the network could page every network base station when paging a device. Obviously, with universal base station paging, the network would incur a great bandwidth cost.
To reduce the paging cost associated with paging a device wireless communications service providers have adopted various strategies. Each of these strategies results in an increase in paging delay—the delay in connecting an intended call recipient to an incoming call—compared to the two paging methods previously mentioned (pages directed to specific cells because of precise location knowledge or universal cell paging). Paging delay is incurred when subsequent rounds of paging are required to reach a user after an initial round of paging. For example, there will be little to no delay with universal paging because every base station is paged during the initial round of paging, thereby guaranteeing that the mobile will be located. However, this will incur large bandwidth costs. In contrast, there typically will be much delay if only a single base station is paged during each round of paging, because the likelihood of reaching the user each round is low. However, this will incur little bandwidth cost. Thus, there is an inherent tradeoff that exists between paging costs and paging delay.
A certain amount of paging delay is tolerable, but as paging delay increases, customer satisfaction decreases as an increasing number of calls get switched to voice mail or the caller hangs up without any connection being made.
Communications service providers thus find it desirable to balance paging costs versus paging delays when operating a communications system.